[Mesa-dev] [PATCH 2/3] radeonsi/nir: Set vs_inputs_dual_locations and let NIR do the remap

[Jason Ekstrand]

We were going out of our way to disable dual-location re-mapping in NIR
only to then do the remapping in st_glsl_to_nir.cpp.  Presumably, this
was so that double_inputs would be correct for the core state tracker.
However, now that we've it to gl_program::DualSlotInputs which is
unaffected by NIR lowering, we can let NIR lower things for us.  The one
tricky bit here is that we have to remap the inputs_read bitfield back
to the single-slot convention for the gallium state tracker to use.

Since radeonsi is the only NIR-capable gallium driver that also supports
GL_ARB_vertex_attrib_64bit, we only have to worry about radeonsi when
making core gallium state tracker changes.
---
 .../nir/nir_lower_io_arrays_to_elements.c     |  5 +--
 src/gallium/drivers/radeonsi/si_get.c         |  1 +
 src/mesa/state_tracker/st_glsl_to_nir.cpp     | 45 +++++++++----------
 3 files changed, 22 insertions(+), 29 deletions(-)

diff --git a/src/compiler/nir/nir_lower_io_arrays_to_elements.c b/src/compiler/nir/nir_lower_io_arrays_to_elements.c
index 16f6233f614..af33d153ea5 100644
--- a/src/compiler/nir/nir_lower_io_arrays_to_elements.c
+++ b/src/compiler/nir/nir_lower_io_arrays_to_elements.c
@@ -36,9 +36,6 @@ static unsigned
 get_io_offset(nir_builder *b, nir_deref_instr *deref, nir_variable *var,
               unsigned *element_index, nir_ssa_def **vertex_index)
 {
-   bool vs_in = (b->shader->info.stage == MESA_SHADER_VERTEX) &&
-                (var->data.mode == nir_var_shader_in);
-
    nir_deref_path path;
    nir_deref_path_init(&path, deref, NULL);
 
@@ -60,7 +57,7 @@ get_io_offset(nir_builder *b, nir_deref_instr *deref, nir_variable *var,
 
          assert(c);     /* must not be indirect dereference */
 
-         unsigned size = glsl_count_attribute_slots((*p)->type, vs_in);
+         unsigned size = glsl_count_attribute_slots((*p)->type, false);
          offset += size * c->u32[0];
 
          unsigned num_elements = glsl_type_is_array((*p)->type) ?
diff --git a/src/gallium/drivers/radeonsi/si_get.c b/src/gallium/drivers/radeonsi/si_get.c
index 90f62edf470..bc3d559861f 100644
--- a/src/gallium/drivers/radeonsi/si_get.c
+++ b/src/gallium/drivers/radeonsi/si_get.c
@@ -497,6 +497,7 @@ static const struct nir_shader_compiler_options nir_options = {
 	.lower_extract_word = true,
 	.max_unroll_iterations = 32,
 	.native_integers = true,
+	.vs_inputs_dual_locations = true,
 };
 
 static const void *
diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index 0ee9bd9fef1..d0ec410ec69 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -32,6 +32,7 @@
 #include "program/prog_parameter.h"
 #include "program/ir_to_mesa.h"
 #include "main/mtypes.h"
+#include "main/imports.h"
 #include "main/errors.h"
 #include "main/shaderapi.h"
 #include "main/uniforms.h"
@@ -83,33 +84,18 @@ st_nir_fixup_varying_slots(struct st_context *st, struct exec_list *var_list)
 static void
 st_nir_assign_vs_in_locations(struct gl_program *prog, nir_shader *nir)
 {
-   unsigned attr, num_inputs = 0;
-   unsigned input_to_index[VERT_ATTRIB_MAX] = {0};
-
-   /* TODO de-duplicate w/ similar code in st_translate_vertex_program()? */
-   for (attr = 0; attr < VERT_ATTRIB_MAX; attr++) {
-      if ((prog->info.inputs_read & BITFIELD64_BIT(attr)) != 0) {
-         input_to_index[attr] = num_inputs;
-         num_inputs++;
-         if ((prog->DualSlotInputs & BITFIELD64_BIT(attr)) != 0) {
-            /* add placeholder for second part of a double attribute */
-            num_inputs++;
-         }
-      } else {
-         input_to_index[attr] = ~0;
-      }
-   }
-
-   /* bit of a hack, mirroring st_translate_vertex_program */
-   input_to_index[VERT_ATTRIB_EDGEFLAG] = num_inputs;
-
    nir->num_inputs = 0;
    nir_foreach_variable_safe(var, &nir->inputs) {
-      attr = var->data.location;
-      assert(attr < ARRAY_SIZE(input_to_index));
-
-      if (input_to_index[attr] != ~0u) {
-         var->data.driver_location = input_to_index[attr];
+      /* NIR already assigns dual-slot inputs to two locations so all we have
+       * to do is compact everything down.
+       */
+      if (var->data.location == VERT_ATTRIB_EDGEFLAG) {
+         /* bit of a hack, mirroring st_translate_vertex_program */
+         var->data.driver_location = _mesa_bitcount_64(nir->info.inputs_read);
+      } else if (nir->info.inputs_read & BITFIELD64_BIT(var->data.location)) {
+         var->data.driver_location =
+            _mesa_bitcount_64(nir->info.inputs_read &
+                              BITFIELD64_MASK(var->data.location));
          nir->num_inputs++;
       } else {
          /* Move unused input variables to the globals list (with no
@@ -743,6 +729,15 @@ st_link_nir(struct gl_context *ctx,
 
       nir_shader_gather_info(nir, nir_shader_get_entrypoint(nir));
       shader->Program->info = nir->info;
+      if (i == MESA_SHADER_VERTEX) {
+         /* NIR expands dual-slot inputs out to two locations.  We need to
+          * compact things back down GL-style single-slot inputs to avoid
+          * confusing the state tracker.
+          */
+         shader->Program->info.inputs_read =
+            nir_get_single_slot_attribs_mask(nir->info.inputs_read,
+                                             shader->Program->DualSlotInputs);
+      }
 
       if (prev != -1) {
          struct gl_program *prev_shader =
-- 
2.17.1